Heat exchanger

ABSTRACT

A heat exchanger includes fins each housed in a respective one of tubes. Each of the fins includes a connecting portion that corrugated for a predetermined fin pitch and that has peaks joined to an inner surface of a wall of each of the tubes and a non-connecting portion that is not joined to the inner surface of the wall of the each of the tubes. The non-connecting portion has a length longer than the predetermined fin pitch. The wall of the each of the tubes has a protrusion to face the non-connecting portion.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of InternationalPatent Application No. PCT/JP2020/009030 filed on Mar. 4, 2020, whichdesignated the U.S. and claims the benefit of priority from JapanesePatent Application No. 2019-045425 filed on Mar. 13, 2019 and JapanesePatent Application No. 2020-021446 filed on Feb. 12, 2020. The entiredisclosures of all of the above applications are incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates to a heat exchanger.

BACKGROUND ART

A condenser includes multiple tubes stacked with each other. Refrigerantis flowing through the tubes. Air is flowing through gaps betweenadjacent ones of the tubes. Inner fins are housed inside the tubes.

SUMMARY

A heat exchanger according to one aspect of the present disclosure hasmultiple tubes stacked with each other and is configured to perform heatexchange between a first fluid flowing inside of the tubes and a secondfluid flowing around the tubes. The heat exchanger includes multiplefins each housed in a respective one of the tubes. Each of the finsincludes a connecting portion and a non-connecting portion. Theconnecting portion is formed by corrugating the each of the plurality offins for a predetermined fin pitch to have a peak that is joined to aninner surface of a wall of each of the plurality of tubes. Thenon-connecting portion has a length longer than the predetermined finpitch. The non-connecting portion is not joined to the inner surface ofthe wall of the each of the tubes. The wall of the each of the tubesincludes a protrusion to face the non-connecting portion.

Further, a heat exchanger according to another aspect of the presentdisclosure has multiple tubes stacked with each other and is configuredto perform heat exchange between a first fluid flowing inside the tubesand a second fluid flowing around the tubes. The heat exchanger includesmultiple fins each housed in a respective one of the tubes. Each of thefins includes a connecting portion and a non-connecting portion. Theconnecting portion is formed by corrugating the each of the fins for apredetermined fin pitch to have a peak that is joined to an innersurface of a wall of each of the tubes. The non-connecting portion has alength longer than the predetermined fin pitch. The non-connectingportion is not joined to the inner surface of the wall of the each ofthe tubes. The non-connecting portion includes a protrusion.

Further, a heat exchanger according to another aspect of the presentdisclosure has multiple tubes stacked with each other and is configuredto perform heat exchange between a first fluid flowing inside the tubesand a second fluid flowing around the tubes. The heat exchanger includesmultiple fins each housed in a respective one of the tubes. Each of thefins includes a connecting portion and a non-connecting portion. Theconnecting portion is formed by corrugating the each of the fins for apredetermined fin pitch to have a peak that is joined to an innersurface of a wall of each of the tubes. The non-connecting portion has alength longer than the predetermined fin pitch. The non-connectingportion is not joined to the inner surface of the wall of the each ofthe tubes. The wall of the each of the tubes includes a protrusion toface the non-connecting portion. The non-connecting portion includes aprotrusion.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view showing a front structure of a heat exchanger ofa first embodiment.

FIG. 2 is a cross-sectional view showing a cross-sectional structuretaken along a line II-II of FIG. 1.

FIG. 3 is a cross-sectional view showing a cross-sectional structure ofa tube of the first embodiment.

FIG. 4 is a perspective view showing a cross-sectional perspectivestructure of the tube of the first embodiment.

FIG. 5 is a graph showing a relationship between the Reynolds number Reof a cooling water and heat transfer coefficient α.

FIG. 6 is a cross-sectional view showing a cross-sectional structure ofa tube of a first modification of the first embodiment.

FIG. 7 is a perspective view showing a cross-sectional perspectivestructure of a tube of the first modification of the first embodiment.

FIG. 8 is a cross-sectional view showing a cross-sectional structure ofa tube of a second embodiment.

FIG. 9 is a cross-sectional view showing a cross-sectional structure ofa tube of a first modification of the second embodiment.

FIG. 10 is a cross-sectional view showing a cross-sectional structure ofa tube of the first modification of the second embodiment.

FIG. 11 is a perspective view showing a cross-sectional perspectivestructure of a tube of a second modification of the second embodiment.

FIG. 12 (A) is a cross-sectional view showing a cross-sectionalstructure around a protrusion of the tube of the second modification ofthe second embodiment.

FIG. 12 (B) is a cross-sectional view showing a cross-sectionalstructure around a protrusion in the tube of the second modification ofthe second embodiment.

FIG. 13 is a schematic diagram showing a flow mode of cooling water inthe tube of the heat exchanger of the second modification of the secondembodiment.

FIG. 14 is a perspective view showing a cross-sectional perspectivestructure of a tube of a third modification of the second embodiment.

FIG. 15 (A) is a cross-sectional view showing a cross-sectionalstructure around a protrusion of the tube of the third modification ofthe second embodiment.

FIG. 15 (B) is a cross-sectional view showing a cross-sectionalstructure around a protrusion of the tube of the third modification ofthe second embodiment.

FIG. 16 is a perspective view showing a cross-sectional perspectivestructure of a tube of a fourth modification of the second embodiment.

FIG. 17 (A) is a cross-sectional view showing a cross-sectionalstructure around a protrusion of the tube of the fourth modification ofthe second embodiment.

FIG. 17 (B) is a cross-sectional view showing a cross-sectionalstructure around a protrusion of the tube of the fourth modification ofthe second embodiment.

FIG. 18 is a cross-sectional view showing a cross-sectional structure ofa tube of another embodiment.

FIG. 19 is a cross-sectional view showing a cross-sectional structure ofa tube of another embodiment.

DESCRIPTION OF EMBODIMENT

To begin with, examples of relevant techniques will be described.

A condenser includes multiple tubes stacked with each other. Refrigerantis flowing through the tubes. Air is flowing through gaps betweenadjacent ones of the tubes. In this condenser, heat exchange isperformed between the refrigerant flowing through the tubes and the airflowing around the tubes, so that the refrigerant is condensed. Innerfins are housed inside the tubes. Each of the inner fins is a so-calledcorrugated fin formed by bending a thin metal plate into a wavy shape.The inner fins have a function of promoting heat exchange between therefrigerant and air by increasing a heat transfer area for therefrigerant.

The structure in which the inner fins are provided inside the tubes isnot limited to the condenser, but is effective for a radiator configuredto cool a cooling water by releasing heat of the cooling water to air.However, when the structure in which inner fins are provided inside thetubes is adopted for the radiator, there are the following concerns.

In recent years, a vehicle traveling with an electric motor as a powersource is sometimes equipped with a radiator for cooling a cooling watercirculating through a battery configured to supply power to the electricmotor and its peripheral devices, in addition to the radiator forcooling the engine cooling water. Such a radiator is sometimes referredto as a low water temperature radiator because cooling water having atemperature lower than that of the engine cooling water flows throughthe radiator. In the low water temperature radiator, a flow rate of thecooling water supplied from an electric pump may be less than that ofthe radiator for engine cooling water. As a result, a flow of thecooling water inside the tubes has a tendency to become the low Re(Reynolds) number flow and heat transfer coefficient of the coolingwater may decrease. Therefore, if inner fins are provided inside thetubes, the heat transfer area for the cooling water can be increased, sothat the heat transfer coefficient of the cooling water can be improved.

In contrast, when the inner fins are provided inside the tubes, theinner fins serve as obstacles to the flow of the cooling water, so thatwater flow resistance of the cooling water increases. Further, when thelow water temperature radiator is mounted in the vehicle, it may benecessary to reduce the number of stacking stages of the tubes of thelow water temperature radiator due to the relationship between spacelimitation of the vehicle and heat generation amount of the low watertemperature radiator. As the number of stacking stages of the tubesdecreases, the flow velocity of the cooling water in the tubesincreases, so that the water flow resistance of the cooling waterfurther increases. When the water flow resistance of the cooling waterincreases, it becomes difficult for the cooling water to flow throughthe tubes, so that the heat transfer coefficient of the low watertemperature radiator may decrease. This is one of the factors that theheat transfer coefficient of the low water temperature radiator cannotbe improved even if the inner fins are provided inside the tubes.

It should be noted that such an issue is not limited to the low watertemperature radiator, but is an issue common to heat exchangers thatexchange heat between the fluid flowing inside the tubes and the fluidflowing around the tubes.

It is an object of the present disclosure to provide a heat exchangercapable of both decreasing water flow resistance and improving heattransfer coefficient.

A heat exchanger according to one aspect of the present disclosure hasmultiple tubes stacked with each other and is configured to perform heatexchange between a first fluid flowing inside of the tubes and a secondfluid flowing around the tubes. The heat exchanger includes multiplefins each housed in a respective one of the tubes. Each of the finsincludes a connecting portion and a non-connecting portion. Theconnecting portion is formed by corrugating the each of the plurality offins for a predetermined fin pitch to have a peak that is joined to aninner surface of a wall of each of the plurality of tubes. Thenon-connecting portion has a length longer than the predetermined finpitch. The non-connecting portion is not joined to the inner surface ofthe wall of the each of the tubes. The wall of the each of the tubesincludes a protrusion to face the non-connecting portion.

According to this configuration, since the non-connecting portions ofthe fins are not in contact with the inner surfaces of the tubes, across-sectional area of a passage through which the first fluid flowscan be secured. Therefore, it is possible to reduce the water flowresistance. Further, since the protrusion formed on the tube increasesthe heat transfer area of the tube for the first fluid, the heattransfer coefficient of the heat exchanger can be improved.

Further, a heat exchanger according to another aspect of the presentdisclosure has multiple tubes stacked with each other and is configuredto perform heat exchange between a first fluid flowing inside the tubesand a second fluid flowing around the tubes. The heat exchanger includesmultiple fins each housed in a respective one of the tubes. Each of thefins includes a connecting portion and a non-connecting portion. Theconnecting portion is formed by corrugating the each of the fins for apredetermined fin pitch to have a peak that is joined to an innersurface of a wall of each of the tubes. The non-connecting portion has alength longer than the predetermined fin pitch. The non-connectingportion is not joined to the inner surface of the wall of the each ofthe tubes. The non-connecting portion includes a protrusion.

According to this configuration, since the non-connecting portions ofthe fins are not in contact with the inner surfaces of the tubes, across-sectional area of a passage through which the first fluid flowscan be secured. Therefore, it is possible to reduce the water flowresistance. Further, since the protrusion is formed on thenon-connecting portion, heat transfer area of the fin for the firstfluid is increased and heat transfer coefficient of the heat exchangercan be improved.

Further, a heat exchanger according to another aspect of the presentdisclosure has multiple tubes stacked with each other and is configuredto perform heat exchange between a first fluid flowing inside the tubesand a second fluid flowing around the tubes. The heat exchanger includesmultiple fins each housed in a respective one of the tubes. Each of thefins includes a connecting portion and a non-connecting portion. Theconnecting portion is formed by corrugating the each of the fins for apredetermined fin pitch to have a peak that is joined to an innersurface of a wall of each of the tubes. The non-connecting portion has alength longer than the predetermined fin pitch. The non-connectingportion is not joined to the inner surface of the wall of the each ofthe tubes. The wall of the each of the tubes includes a protrusion toface the non-connecting portion. The non-connecting portion includes aprotrusion.

According to this configuration, since the non-connecting portions ofthe fins are not in contact with the inner surfaces of the tubes, across-sectional area of a passage through which the first fluid flowscan be secured. Therefore, it is possible to reduce the water flowresistance. Further, since the protrusions formed on the tubes and theprotrusions formed on the non-connecting portions of the fins increasethe heat transfer area of the tubes and fins for the first fluid, theheat transfer coefficient of the heat exchanger can be improved.

Hereinafter, an embodiment of a heat exchanger will be described withreference to the drawings. To facilitate understanding, identicalconstituent elements are designated with identical symbols in thedrawings where possible with the duplicate description omitted.

First Embodiment

First, a heat exchanger 10 of a first embodiment shown in FIG. 1 will bedescribed. The heat exchanger 10 shown in FIG. 1 is mounted on a vehicleequipped with an internal combustion engine and an electric motor as adriving power source. Through the heat exchanger 10, an engine coolingwater for cooling the internal combustion engine and a cooling water forcooling the electric motor and its peripheral devices circulate. Sincethe cooling water for cooling the electric motor and its peripheraldevices has a temperature lower than that of the engine cooling water,it will be hereinafter referred to as “a low temperature cooling water”.The heat exchanger 10 is a complex radiator that is configured to coolboth the engine cooling water and the low temperature cooling waterthrough a heat exchange between the engine cooling water and air andheat exchange between the low temperature cooling water and air. In thepresent embodiment, the engine cooling water and the low temperaturecooling water correspond to a first fluid, and the air corresponds to asecond fluid. Hereinafter, the engine cooling water and the lowtemperature cooling water are collectively referred to as “a coolingwater”. The heat exchanger 10 is arranged in an engine compartmenttogether with a condenser and an evaporator of a vehicular airconditioner. For example, in case of a combination with the evaporatorof the vehicular air conditioner, the heat exchanger 10 is arranged at aposition closer to a grill opening than the condenser of the vehicularair conditioner is. Air introduced through the grill opening is suppliedto the heat exchanger 10.

As shown in FIG. 1, the heat exchanger 10 includes a core portion 20, afirst header tank 30, and a second header tank 40.

The core portion 20 includes multiple tubes 21 and multiple outer fins22.

The multiple tubes 21 are stacked at predetermined intervals in adirection indicated by an arrow Z. The tubes 21 extend in a directionindicated by an arrow X. A cross-sectional shape of each of the tubes 21perpendicular to the direction shown by the arrow X has a flat tubularshape. The tubes 21 define therein passages extending in the directionshow by the arrow X and the cooling water flows through the passages.Air flows through gaps between adjacent ones of the tubes 21 in adirection indicated by an arrow Y.

Hereinafter, the direction indicated by the arrow X is referred to as “atube longitudinal direction X”, the direction indicated by the arrow Yis referred to as “an airflow direction Y”, and the direction indicatedby the arrow Z is referred to as “a tube stacking direction Z”. In thepresent embodiment, the tube stacking direction Z is a verticaldirection, and the tube longitudinal direction X and the airflowdirection Y are horizontal directions. Therefore, the heat exchanger 10of the present embodiment is a so-called cross-flow heat exchanger.

The outer fins 22 are arranged in the gaps between the adjacent ones ofthe tubes 21. Each of the outer fins 22 are a so-called corrugated finformed by bending a thin metal plate made of aluminum or the like into awavy shape. Peaks of bending portions of each of the outer fin 22 are incontact with and brazed to outer surfaces of the adjacent ones of thetubes 21. The outer fins 22 are fixed to the tubes 21 by this jointstructure. The outer fins 22 have a function of promoting heat exchangebetween the refrigerant flowing inside the tubes 21 and the air flowingthrough the gaps between the adjacent ones of the tubes 21 by increasinga heat transfer area for the air.

The first header tank 30 is connected to one end of each of the tubes21. The first header tank 30 is formed into a tubular shape. The firstheader tank 30 includes therein a partition 33 that partitions aninternal space of the first header tank 30 into a first distributionpassage 31 and a second distribution passage 32. The first header tank30 defines a first inlet 310 at a portion defining the firstdistribution passage 31 and a second inlet 320 at a portion defining thesecond distribution passage 32.

The second header tank 40 is connected to the other end of each of thetubes 21. The second header tank 40 is formed into a tubular shape likethe first header tank 30. The second header tank 40 defines therein apartition 43 that partitions the inner space into a first mergingpassage 41 and a second merging passage 42. The partition 43 of thesecond header tank 40 is arranged at the same position as the positionof the partition 33 of the first header tank 30 in the tube stackingdirection Z. The second header tank 40 defines a first outlet 410 at aportion defining the first merging passage 41 and a second outlet 420 ata portion defining the second merging passage 42.

In the following, a region of the core portion 20 connected to the firstdistribution passage 31 of the first header tank 30 and the firstmerging passage 41 of the second header tank 40 will be referred to as afirst core region A1. Similarly, a region of the core portion 20connected to the second distribution passage 32 of the first header tank30 and the second merging passage 42 of the second header tank 40 willbe referred to as a second core region A2. As shown in FIG. 1, in theheat exchanger 10 of the present embodiment, the first core region A1 islarger than the second core region A2.

In the heat exchanger 10, the engine cooling water flows into the firstinlet 310 of the first header tank 30. The engine cooling water havingflowed into the first inlet 310 are distributed to each of the tubes 21in the first core region A1 of the core portion 20 from the firstdistribution passage 31 of the first header tank 30. In the first coreregion A1 of the core portion 20, the engine cooling water is cooled byheat exchange between the engine cooling water flowing inside the tubes21 and the air flowing around the tubes 21. The engine cooling watercooled by flowing through the tubes 21 merges in the first mergingpassage 41 of the second header tank 40 and then flows out of the secondheader tank 40 through the first outlet 410.

Further, in the heat exchanger 10, the low water temperature coolingwater flows into the first header tank 30 through the second inlet 320.The low water temperature cooling water having flowed into the secondinlet 320 is distributed from the second distribution passage 32 of thefirst header tank 30 to each of the tubes 21 in the second core regionA2 of the core portion 20. In the second core region A2 of the coreportion 20, the low water temperature cooling water is cooled by heatexchange between the low water temperature cooling water flowing insidethe tubes 21 and the air flowing around the tubes 21. The low watertemperature cooling water cooled when flowing through the tubes 21 mergein the second merging passage 42 of the second header tank 40 and thenflows out of the second header tank 40 through the second outlet 420.

Next, a structure of the core portion 20 will be specifically described.

As shown in FIG. 2, in the core portion 20, a stacking structure of thetubes 21 are arranged in two rows in the airflow direction Y. The coreportion 20 is not limited to a structure having two rows of stackingstructures of the tubes 21, and may be a structure having only one rowof the stacking structure of the tubes 21.

Inner fins 23 are housed inside the tubes 21. Each of the inner fins 23is formed by bending a thin metal plate such as aluminum.

As shown in FIGS. 3 and 4, the inner fin 23 has a deformed portion 232at one end of the inner fin 23. The deformed portion 232 is deformed tobe fixed to the tube 21. Due to the deformed portion 232, a thickness ofone end of the tube 21 is increased, so that resistance of the tube 21against stone chipping is secured.

The inner fin 23 includes connecting portions 230 a, 230 b, and 230 ceach of which is formed by bending the metal plate into a wavy shape tohave a predetermined fin pitch FP. The connecting portion 230 a isformed at an inner side of the deformed portion 232, the connectingportion 230 b is formed at a center portion of the inner fin 23, and theconnecting portion 230 a is formed at the other end portion of the innerfin 23. Peaks of the connecting portions 230 a to 230 c are in contactwith an inner surface of the tube 21. A contact portion between thepeaks and the inner surface of the tube 21 are brazed to each other. Theconnecting portions 230 a to 230 c position the inner fin 23 withrespect to the tube 2, secure heat transfer area to the tube 21, andsecure rigidity of the tube 21.

The inner fin 23 includes non-connecting portion 231 a between theconnecting portion 230 a and the connecting portion 230 b. Thenon-connecting portion 231 a is not joined to the inner surface of thetube 21. Similarly, the inner fin 23 includes a non-connecting portion231 b between the connecting portion 230 b and the connecting portion230 c. The non-connecting portions 231 a and 231 b extend parallel tothe inner surface of the tube 21. The non-connecting portion 231 a has alength L1 and the non-connecting portion 231 b has a length L2. Each ofthe length L1 and the length L2 is longer than the fin pitch of theconnecting portions 230 a to 230 c.

The tube 21 includes multiple protrusions 210 a and 211 a protrudinginto the tubes 21 to face the non-connecting portions 231 a and 231 b.More specifically, one of an outer surface of the tube 21 facing thenon-connecting portion 231 a of the inner fin 23 includes multiple firstprotrusions 210 a. The other of the outer surface of the tube 21 facingthe non-connecting portion 231 a of the inner fin 23 includes multiplesecond protrusions 211 a. The first protrusions 210 a are arranged atpositions closer to the connecting portion 230 a than the connectingportions 230 b of the inner fin 23. The second protrusions 211 a arearranged at positions closer to the connecting portion 230 b than theconnecting portions 230 a of the inner fin 23. Similarly, outer wallportions 210 and 211 of the tube 21 facing the non-connecting portion231 b of the inner fin 23 includes the first protrusions 210 a and thesecond protrusion 211 a. A first space S1 is defined as a spacepartitioned by the connecting portions 230 a and 230 b of the inner fin23, the non-connecting portion 231 a, and the outer wall portions 210and 211 of the tube 21. A second space S2 is defined as a spacepartitioned by the connecting portions 230 b and 230 c of the inner fin23, the non-connecting portion 231 b, and the outer wall portions 210and 211 of the tubes 21. In this case, the first space S1 hassubstantially the same shape as the second space S2.

Next, an operation example of the heat exchanger 10 of the presentembodiment will be described.

In the heat exchanger 10 of the present embodiment, the Reynolds numberRe of the cooling water flowing through the tubes 21 and the heattransfer coefficient α of the cooling water change as shown by the solidline L1 in FIG. 5. In FIG. 5, as a reference example, a chain line L2shows a relationship between the Reynolds number Re and the heattransfer coefficient α of the cooling water in case that the tubes 21does not include the protrusions 210 a and 211 a and that the inner fins23 are not disposed in the tubes 21. Further, in FIG. 5, as a referenceexample, a chain double dashed line L3 shows a relationship between theReynolds number Re and the heat transfer coefficient of the coolingwater in case that the tubes 21 include the protrusions 210 a and 211 band that the inner fins 23 are not disposed in the tubes 21.

As shown in FIG. 5, when the value of the Reynolds number Re is small,the cooling water becomes a laminar flow. Further, when the value of theReynolds number Re is large, the cooling water becomes a turbulent flow.When the value of the Reynolds number Re is an intermediate valuebetween them, the flow of the cooling water is within a transition zone.The transition zone is a zone in which the flow of the cooling water istransitioned between the laminar flow and the turbulent flow

As shown by the chain double dashed line L3 in FIG. 5, in case that thetubes 21 include the protrusions 210 a and 211 a and the inner fins 23are not disposed in the tubes 21, the heat transfer coefficient α of thecooling water can be secured when the cooling water in the transitionflow zone or the turbulent flow zone. However, when the cooling water isin the laminar flow zone, there is a possibility that the heat transfercoefficient α of the cooling water cannot be sufficiently secured.Compared the flow rate of the engine cooling water flowing through thefirst core region A1, the flow rate of the low temperature cooling waterflowing through the second core region A2 of the heat exchanger 10 islower. Thus, the flow of the low-temperature cooling water flowingthrough the second core region A2 of the heat exchanger 10 tends to be alayer flow. Therefore, the heat transfer coefficient α may not besufficiently secured only by forming the protrusions 210 a and 211 b inthe tubes 21.

In this regard, in the heat exchanger 10 of the present embodiment, asshown by the solid line L1 in FIG. 5, the heat transfer coefficient α ofthe cooling water in the laminar flow zone can be improved compared withthe reference example shown by the chain double dashed line L3. This isbecause, in the heat exchanger 10 of the present embodiment, the heattransfer area is increased and the heat transfer can be promoted by theinner fins 23 provided inside the tubes 21.

Further, in the heat exchanger 10 of the present embodiment, the heattransfer coefficient α of the cooling water can be improved in thetransition zone as shown in the solid line L1 compared with thereference example shown by the chain double dashed line L3. This isbecause, in addition to the effects of the protrusions 210 a and 211 athemselves, the inner fins 23 can increase the heat transfer area andpromote heat transfer.

According to the heat exchanger 13 of the present embodiment describedabove, operations and effects described in the following items (1) to(5) can be obtained.

(1) Since the non-connecting portions 231 a and 231 b of the inner fins23 are not in contact with the inner surfaces of the tubes 21,cross-sectional areas of passages through which the engine cooling waterand the low temperature cooling water flow can be secured. Thus, it ispossible to reduce water flow resistance. Further, the protrusions 210 aand 211 a formed on the tubes 21 locally increase heat transfer areabetween the tubes 21 and the cooling water and improve the heat transfercoefficient of the heat exchanger 10 by having the cooling water aroundthe protrusions flow turbulently.

(2) The protrusions 210 a and 211 a protrude into the tubes 21.According to such a configuration, it is possible to avoid interferencebetween the protrusions 210 a and 211 a and the outer fins 22.

(3) The non-connecting portions 231 a and 231 b extend in parallel tothe inner surface of the tubes 21. According to such a configuration,passages having a predetermined width can be secured between thenon-connecting portion 231 a and 231 b of the inner fin 23 and the innersurface of the tube 21, so that a water resistance of the cooling waterflowing through the tube 21 can be further reduced.

First Modification

Next, a first modification of the heat exchanger 13 of the firstembodiment will be described.

As shown in FIG. 6, the tube 21 of this modification include theprotrusions 210 a and 211 a protruding outward.

According to such a configuration, the air flowing through gaps betweenthe adjacent ones of the tubes 21 collides with the protrusions 210 aand 211 a, so that the airflow direction around the tubes 21 can bechanged. As a result, the air is assisted to flow into louvers formed inthe outer fins 22 and the protrusions 210 a and 211 b can improve heattransfer performance for the air.

Second Modification

Next, a heat exchanger 13 of a second modification of the firstembodiment will be described.

As shown in FIG. 7, a shape of each of protrusions 210 a and 211 a ofthis modification is not hemispherical but an elongated shape extendingin a direction diagonally intersecting the flow direction of the coolingwater. According to such a configuration, it is possible to minimizegaps formed between connecting surfaces of the outer fins 22 and theprotrusions 210 a and 211 a. As a result, the connecting area betweenthe tubes 21 and the outer fins 22 are increased and heat transferperformance can be improved for the cooling water and the air.

Second Embodiment

Next, a heat exchanger 13 of a second embodiment will be described.Hereinafter, differences from the heat exchanger 13 of the firstembodiment will be mainly described.

As shown in FIG. 8, in the heat exchanger 10 of the present embodiment,each of the non-connecting portions 231 a and 231 b includes multipleprotrusions 232 a. The protrusions 232 a are formed not to be in contactwith the inner surface of the tube 21. An arrangement of the protrusions232 a in the non-connecting portion 231 a is substantially the same asan arrangement of the protrusions 232 a in the non-connecting portion231 b. As a result, when a first space 51 is defined as a spacepartitioned by the connecting portions 230 a and 230 b of the inner fin23, the non-connecting portion 231 a, and the outer wall portions 210and 211 and a second space S2 is defined as a space partitioned by theconnecting portions 230 b and 230 c, the non-connecting portion 231 b,and the outer wall portions 210 and 211, the first space 51 hassubstantially the same shape as the second space S2.

According to the heat exchanger 10 of the present embodiment describedabove, the following advantages shown in (4) can be obtained in additionto the advantages shown in (3) above.

(4) Since the non-connecting portions 231 a and 231 b are not in contactwith the inner surface of the tube 21, cross-sectional areas of thepassages through which the engine cooling water and the low temperaturecooling water flow can be secured. Therefore, it is possible to reducethe water flow resistance. Further, since the protrusions 232 a formedon the inner fin 23 increase the heat transfer area of the inner fin 23with respect to the cooling water, the heat transfer coefficient of theheat exchanger 10 can be improved. Although it is desirable that all ofthe protrusions 232 a be not in contact with the inner surface of thetube 21, a part of the protrusions 232 a may be in contact with theinner surface of the tube 21 as long as the same or similar advantagesas those of the heat exchanger 10 of the present embodiment can beobtained.

First Modification

Next, a heat exchanger 13 of a first modification of the secondembodiment will be described.

As shown in FIG. 9, in the heat exchanger 10 of the presentmodification, the inner fin 23 includes protrusions 232 a which areformed by cutting and bending a part of the non-connecting portions 231a and 231 b into a trapezoidal shape. The cut-up shape of theprotrusions 232 a is not limited to the trapezoidal shape, and may betriangular, for example, as shown in FIG. 10.

According to such a configuration, the protrusions 232 a can be easilyformed on the inner fin 23.

Second Modification

Next, a heat exchanger 13 of a second modification of the secondembodiment will be described. In the following, as shown in FIG. 11, onedirection in the tube longitudinal direction X is referred to as a X1direction, and the other direction in the tube longitudinal direction isreferred to as a X2 direction. Further, one direction in the airflowdirection Y is referred to as a Y1 direction, and the other direction inthe airflow direction Y is referred to as a Y2 direction. Further, onedirection in the tube stacking direction Z is referred to as a Z1direction, and the other direction in the tube stacking direction isreferred to as a Z2 direction. The X2 direction corresponds to a flowdirection of the cooling water.

As shown in FIG. 11, in the heat exchanger 10 of this modification, theinner fin 23 includes protrusions 232 b and 232 c in the non-connectingportions 232 b and 232 c.

The protrusions 232 b protrude from the non-connecting portions 231 aand 231 b in the Z2 direction. The protrusions 232 b extend in adirection that a component in the X2 direction and a component in the Y2direction are combined.

The protrusions 232 c protrude from the non-connecting portions 231 aand 231 b in the Z1 direction. The protrusions 232 c extend in adirection that a component in the X2 direction and a component in the Y2direction are combined.

As shown in FIGS. 12A and 12B, each of the protrusions 232 b and 232 care formed not to be in contact with the outer wall portions 210 and 211of the tube 21.

Next, an operation example of the heat exchanger 10 of this modificationwill be described.

When the protrusions 232 c are formed on the inner fin 23, the flowdirection of the cooling water flowing inside the tube 21 can be changedas shown by an arrow in FIG. 13, for example. Note that FIG. 13illustrates a case where the cross-sectional shape of the protrusions232 c is trapezoidal. As shown in FIG. 13, when the cooling waterreaches the protrusion 232 c, the cooling water flows along an outersurface of the protrusion 232 c, so that the flow direction of thecooling water flowing inside the outer wall portion 210 of the tube 21is changed in the direction Z1. As a result, the cooling water flowstoward the inner surface of the tube 21 to collide with the inner wallsurface of the tube 21, so that heat exchange is easily performedbetween the inner wall surface of the tube 21 and the cooling water. Thesame action and effect are exhibited at the protrusions 232 c. As aresult, the heat exchange between the air flowing through the outer fins22 and the cooling water flowing inside the tube 21 can be furtherpromoted, so that the heat transfer coefficient of the heat exchanger 10can be improved. Although it is desirable that all of the protrusions232 b and 232 c be not in contact with the outer wall portions 210 and211 of the tube 21, a part of the protrusions 232 b and 232 c may be incontact with the outer wall portions 210 and 211 of the tube 21 as longas the same or similar advantages as those of the heat exchanger 10 inthis embodiment can be obtained.

Further, as shown in FIG. 11, the protrusions 232 c protruding in the Z2direction and the protrusions 232 c protruding in the Z1 direction arealternately arranged in the X2 direction in the tube 21 of the presentmodification, in other words, in the flow direction of the coolingwater. Thus, the cooling water discontinuously and alternately collideswith the inner surface in the Z1 direction and in the Z2 direction. As aresult, the heat transfer coefficient of the heat exchanger 10 can beimproved while reducing the pressure loss of the cooling water.

Third Modification

Next, a heat exchanger 13 of a third modification of the secondembodiment will be described.

As shown in FIGS. 14, 15 (A), and 15 (B), in the heat exchanger 10 ofthis modification, each of the protrusions 232 b and 232 c has aso-called fish shadow streamline shape in which a protruding lengthincreases in the X1 direction, i.e., toward an upstream side in the flowdirection of the cooling water. The shapes of the protrusions 232 b and232 c are also referred to as tilted blade shapes.

Next, an operation example of the heat exchanger 10 of this modificationwill be described.

When the cooling water flows as shown by arrows in FIG. 13, the coolingwater having passed through the protrusion 232 b tends to flowseparately from the inner fin 23. This is a factor to reduce the heattransfer area of the cooling water in the inner fin 23.

In this regard, if the protrusions 232 are formed in a streamlined shapelike the heat exchanger 10 of this modification, the cooling waterhaving passed through the protrusions 232 b and 232 c tends to flowalong the inner fin 23. Thus, it is possible to suppress a decrease inthe heat transfer area of the cooling water in the inner fin 23.

Fourth Modification

Next, a heat exchanger 13 of a fourth modification of the secondembodiment will be described.

As shown in FIGS. 16, 17 (A) and 17 (B), in the heat exchanger 10 ofthis modification, cross-sectional shapes of the protrusions 232 b and232 c orthogonal to the directions Z1 and Z2 are circular. According tosuch a configuration, the cooling water easily flows along the peripheryof the protrusions 232 b and 232 c, so that the cooling water is lesslikely to separate from the protrusions 232 b and 232 c. As a result,the heat transfer coefficient around the protrusions 232 b and 232 c ofthe inner fin 23 can be locally improved.

OTHER EMBODIMENTS

The preceding embodiments may be practiced in the following modes. Inthe heat exchanger 10 of each embodiment, the first space S1 is definedas the space partitioned by the connecting portions 230 a and 230 b, thenon-connecting portion 231 a of the inner fin 23, and the outer wallportions 210 and 211 of the tube 21 and the second space S2 is definedas the space partitioned by the connecting portions 230 b and 230 c, thenon-connecting portion 231 b of the inner fin 23, and the outer wallportions 210 and 211 of the tube 21. In this case, a shape of the firstspace S1 may be symmetrical with the second space S2 with respect to acenter line of the tube 21 in the airflow direction Y. According to sucha configuration, the cooling water can flow more uniformly in theinternal passage of the tube 21.

The inner fin 23 of the first embodiment may have multiple protrusions210 a and 211 a formed line-symmetrically with respect to the centerline in the airflow direction Y. Further, the multiple protrusions 210 aand 211 a may be arranged in a staggered pattern or a grid pattern.

The configuration of the heat exchanger 10 of this embodiment can beapplied to any heat exchanger. Applicable heat exchangers include, forexample, heat exchangers in which only one type of fluid flows,small-sized down-face heat exchangers, medium-sized half-face heatexchangers, and large-sized full-face heat exchangers. Further, the flowdirection of the cooling water in the heat exchanger 10 can be changedas appropriate. For example, as the heat exchanger 10, it is alsopossible to adopt a so-called down-flow type heat exchanger in which thecooling water flows in the vertical direction.

The configuration of the heat exchanger 10 of each embodiment is notlimited to the radiator that cools the cooling water, and can be appliedto any heat exchanger such as a condenser configured to condense therefrigerant through heat exchange between air and the refrigerant. Whenthe configuration of the heat exchanger 10 of each embodiment is appliedto the condenser, the refrigerant corresponds to the first fluid and theair corresponds to the second fluid.

As shown in FIG. 18, in the heat exchanger 10, the protrusions 210 a and211 a may be formed on the tube 21 and the protrusions 232 a and 232 amay be formed on the inner fin 23. Further, the tube 21 may have astructure in which the tip ends of the tube 21 do not hold the inner fin23.

As shown in FIG. 19, in the heat exchanger 10 of the first embodiment,the protrusions 210 a and 211 a of the tube 21 may be in contact withthe inner fins 23. Further, in the heat exchanger 10 of the secondembodiment, the protrusions 232 a of the inner fin 23 may be in contactwith the inner surface of the tube 21.

The number of protrusions 210 a, 211 a formed on the tube 21 of thefirst embodiment and the number of the connecting portions 230 a, 230 b,and 230 c formed on the inner fin 23 can be arbitrarily changed.Further, the number of protrusions 232 a, 232 b, 232 c formed on theinner fin 23 of the second embodiment and the number of the connectingportions 230 a, 230 b, and 230 c can be arbitrarily changed.

The present disclosure is not limited to the specific examples describedabove. The specific examples described above which have beenappropriately modified in design by those skilled in the art are alsoencompassed in the scope of the present disclosure so far as themodified specific examples have the features of the present disclosure.Each element included in each of the specific examples described above,and the placement, condition, shape, and the like of the element are notlimited to those illustrated, and can be modified as appropriate. Thecombinations of the elements in each of the specific examples describedabove can be changed as appropriate, as long as it is not technicallycontradictory.

What is claimed is:
 1. A heat exchanger comprising: a plurality of tubes stacked with each other, a heat exchange being performed between a first fluid flowing through the plurality of tubes and a second fluid flowing around the plurality of tubes; and a plurality of fins each housed in a respective one of the plurality of tubes, wherein each of the plurality of fins includes: a connecting portion that is corrugated for a predetermined fin pitch and that has peaks joined to an inner surface of a wall of each of the plurality of tubes; and a non-connecting portion that is not corrugated for the predetermined fin pitch and that is not joined to the inner surface of the wall of the each of the plurality of tubes, the non-connecting portion having a length longer than the predetermined fin pitch, wherein the wall of the each of the plurality of tubes has a protrusion to face the non-connecting portion.
 2. The heat exchanger according to claim 1, wherein the protrusion protrudes inward from the wall of the each of the plurality of tubes.
 3. The heat exchanger according to claim 1, wherein the protrusion is not in contact with the each of the plurality of fins.
 4. The heat exchanger according to claim 1, wherein the protrusion protrudes outward from the wall of the each of the plurality of tubes.
 5. A heat exchanger comprising: a plurality of tubes stacked with each other, a heat exchange being performed between a first fluid flowing through the plurality of tubes and a second fluid flowing around the plurality of tubes; and a plurality of fins each housed in a respective one of the plurality of tubes, wherein each of the plurality of fins includes: a connecting portion that is corrugated for a predetermined fin pitch and that has peaks joined to an inner surface of each of the plurality of tubes; and a non-connecting portion that is not corrugated for the predetermined fin pitch and that is not joined to the inner surface of the each of the plurality of tubes, the non-connecting portion having a length longer than the predetermined fin pitch, wherein the non-connecting portion includes a protrusion.
 6. The heat exchanger according to claim 5, wherein the protrusion is formed by cutting and bending a portion of the non-connecting portion.
 7. The heat exchanger according to claim 5, wherein the protrusion is not in contact with the inner surface of the each of the plurality of tubes.
 8. The heat exchanger according to claim 1, wherein the non-connecting portion extends parallel to the inner surface of the each of the plurality of tubes.
 9. A heat exchanger comprising: a plurality of tubes stacked with each other, a heat exchange being performed between a first fluid flowing through the plurality of tubes and a second fluid flowing around the plurality of tubes; and a plurality of fins each housed in a respective one of the plurality of tubes, wherein each of the plurality of fins includes: a connecting portion that is corrugated for a predetermined fin pitch and that has peaks joined to an inner surface of a wall of each of the plurality of tubes; and a non-connecting portion that is not corrugated for the predetermined fin pitch and that is not joined to the inner surface of the wall of the each of the plurality of tubes, the non-connecting portion having a length longer than the predetermined fin pitch, wherein the wall of the each of the plurality of tubes includes a protrusion to face the non-connecting portion, and the non-connecting portion includes a protrusion.
 10. A heat exchanger comprising: a plurality of tubes stacked with each other, a heat exchange being performed between a first fluid flowing through the plurality of tubes and a second fluid flowing around the plurality of tubes; and a plurality of fins each housed in a respective one of the plurality of tubes, wherein each of the plurality of fins includes: a connecting portion that is corrugated for a predetermined fin pitch and that has peaks joined to an inner surface of a wall of each of the plurality of tubes; and a non-connecting portion that is not joined to the inner surface of the wall of the each of the plurality of tubes, the non-connecting portion having a length longer than the predetermined fin pitch, wherein the wall of the each of the plurality of tubes includes a protrusion to face the non-connecting portion, and the protrusion protrudes inward from the wall of the each of the plurality of tubes. 